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I recently got a Fiddlerman Concert violin complete with carbon fiber bow, which is a huge improvement in sound and playability from the cheap Cecilio bows I'd used before. However...I've always been told that you should tighten the bow until the gap between the hair and the tightest part of the bow curve is approximately the diameter of a pencil, and in fact do use a pencil to check when I tighten the bow before each practice session. That works when I play with the bow flat on the strings; but if I tilt the bow slightly forward (toward the scroll), I find that the stick will often hit the strings when I play a note forcefully, and especially if I have to play double-stops. Should I be tightening the bow a bit more so that that doesn't happen, stop playing with so much force (which doesn't seem particularly excessive to me), or just accept that the stick may hit the strings on occasion? (The latter seems pretty far-fetched, but those seem to me the only alternatives to come to mind.)
Well... you don't actually get maximum volume by pressing the bow hard into the string. Excessive bow pressure can choke the sound. In general, violinists should rely mainly on bow speed and very little on bow pressure. You'd be surprised at how much sound you can get out of a violin with very little pressure at all.
Also, when playing fortissimo, you should probably be playing with the bow hair flat on the strings, which is only a small hand and wrist adjustment.
That's my point -- my "forcefully" is far from ff. Frankly, it might not even be an f -- it just isn't a p! What I'm trying to say is that the only way I don't get the stick hitting the strings with any tilt at all is if I'm consciously trying to play very softly, with a very light touch; but I get the sense from most people that you should be playing with at least a little tilt even on mf notes.
I have found that when I play with my favorite carbon fiber bow, I need to tension it more than a "pencil" width to play with it effectively. Not sure if is is because of the horse hair being older or the moisture in my room. All I can say for sure is that the pencil measurement doesn't work for that particular bow. I need to tighten it to one of those big 1st grader pencils lol. Another possibility is that the carbon fiber relaxes more than some other bows. Couldn't hurt to try tightening it a bit more to see if you like the results better. I had to experiment with mine until I found a place in tension I liked.
What Andrew says is correct. I would only add that different violins will be varying degrees of volume using the same bow techniques.
For me how much I tighten the bow isn't always an exact measurement. Not to sound to technical..but sometimes if I'm practicing say something faster with ornaments I'll experiment with less tension and slower type stuff where tone stands out even more I'll tighten a little more. I'm usually judging by the sound I'm getting and how much the bow wants to bounce. all of this is more of an eyeball type measurement based on what's been working for me. I'm thinking for a carbon bow that it would tend to be more repeatable than with a wood bow, but that's a thought for conversation not a fact based on experience. Not suggesting what I'm doing is the way just sharing what Ive discovered works for me so far.